Variable timing control for ARCP voltage source inverters operating at low DC voltage

The Auxiliary Resonant Commutated Pole (ARCP) inverter has been of interest in motor drive applications that can benefit from any combination of increased conversion efficiency, reduced EMI radiation, or higher PWM switching frequency. The ARCP inverter achieves high efficiency by turning the main switches on or off only under zero-voltage conditions. This reduces switching losses in the main circuit, and potentially increases overall conversion efficiency. Furthermore, the reduced loss in the main switch offers opportunity for higher switching frequencies, which is of benefit for ironless low-inductance motors that are widely being used in small to medium power vehicle propulsion applications. The soft-switching ARCP generates an output with significantly reduced dv/dt and di/dt as compared to hard-switched inverters, which tends to reduce EMI emissions. All of these attributes of the soft-switching ARCP are potentially beneficial in electric propulsion or electric vehicle auxiliary applications. In the ARCP inverter, the control signal timing for main and auxiliary switches is critical to maintain the most favorable operating conditions. Many ARCP implementations utilize a variable timing control, where load current polarity and magnitude are used to determine the control signal timing - usually without additional sensors. In this paper, the timing of main and auxiliary switching is examined for low dc bus voltage operation. A variable timing methodology for ARCP switching will be developed specifically to address issues associated with low-voltage ARCP operation. The operation principles are described, and simulation and experimental results are included to demonstrate the approach.